1. Field
The present disclosure generally relates to controlling thickness, and more particularly thickness variation, in a glass ribbon as the ribbon is produced, wherein sheets are subsequently separated from the ribbon.
2. Technical Background
A muffle door is used to control thickness gradients in a glass ribbon, from which there are separated glass sheets for making displays—for example, LCDs, plasma displays, OLEDs, and/or electroluminescent displays—and is generally described in U.S. Pat. No. 3,682,609. Air is blown through a bank of tubes of specific diameter a specific distance from a front plate designed of high thermal conductivity material that faces glass that is at a temperature above its softening point temperature. The objective is to generate thermal gradients across the ribbon, perpendicular to the direction of glass flow. These thermal gradients change the localized viscosity of the glass in one area relative to another, impacting the attenuation of the glass, and thus local thickness, from a downward pull force. The air that discharges from these tubes circulates in a muffle door housing and is designed to dissipate out through venting holes 180° from where the air exits the bank of tubes near the front plate.